In recent years, electronic devices have been required to have reduced thickness, reduced weight, and flexibility due to rapid progress in displays such as a crystal liquid display, an organic EL display, and an electronic paper, as well as an organic solar cell, a secondary battery, a semiconductor, a touch panel, and the like. In view of this, in order to achieve the reduced thickness, reduced weight, and flexibility, it has been considered to use a thin substrate and a thin functional coating layer formed on the substrate in an electronic device.
Moreover, as a method of producing such an electronic device, it has been considered to employ a roll-to-roll process in order to achieve low cost.
Since aluminum (Al), which is light in weight and is excellent in heat resistance, can be a thin and flexible material that can be subjected to the roll-to-roll process when it is in the form of a foil, aluminum has been drawing attention as the substrate of the above-described electronic device or a carrier member used for the roll-to-roll process. It should be noted that regarding the surface smoothness of the aluminum foil, a surface roughness Ra thereof is about 0.04 μm in a measurement based on JIS B0601 (1982) as described in Japanese Patent Laying-Open No. 2013-045788 (Patent Document 1).